This invention relates to antimicrobial compositions. In particular, this invention relates to synergistic antimicrobial compositions offering superior performance, containing combinations of furanones with other disinfectants, such as, for example, quaternary ammonium compounds and/or organosilanes with quaternary ammonium functionality (xe2x80x9cquaternized organosilanesxe2x80x9d). Additionally, biguanides and disinfectant amines also may be advantageously combined with furanones in an antimicrobial composition.
Mold, mildew and bacterial contamination are undesirable on many types of surfaces. Control of such biological fouling has largely been based on the use of biocides that may have a harmful effect on the environment. However, the use of natural biocides or derivatives thereof that are environmentally acceptable is becoming increasingly desirable and necessary.
The bacterial properties of quaternary ammonium compounds are generally known. Such compounds have been used extensively in cleaning compositions for domestic and industrial applications. However, it would be preferable to use small amounts of these compounds in cleaning compositions since they can be harmful to the environment in large amounts.
Quaternized organosilanes also have antimicrobial activity, and can be used to treat mold and mildew in buildings; however, it is necessary to stabilize them before they can be used in cleaning compositions. U.S. Pat. No. 5,411,585 to Avery, et al. teaches that certain organosilanes containing hydrolyzable groups, especially quaternized organosilanes, can form clear solutions in aqueous media that are stable over extended periods of time. These solutions are formed without the use of emulsion technology involving the application of high shear forces, by further including a water soluble organic, non-silicon quaternary ammonium compound along with nonionic, amphoteric, sarcosine anionic or certain cationic surfactants. U.S. Pat. No. 6,087,319 also teaches that organosilanes, including quaternized organosilanes, can be stabilized using saccharides, sometimes with an additional nonionic co-surfactant. Stabilized organosilanes remain stable over a broad pH range. They can then be particularly useful as coupling agents in household and industrial cleaning compositions where an antimicrobial and soil-releasing substrate is desired. However, given that quaternized organosilanes are expensive, it may not be economical to use this compound exclusively to impart antimicrobial activity to a household or industrial cleaning solution.
Certain furanones, particularly halogenated furanones, which can be derived from natural sources, such as seaweed, or synthesized, are also known to inhibit the growth of microorganisms.
U.S. Pat. No. 6,060,046 relates to an antifouling composition that comprises an effective amount of a halogenated furanone compound having a specified structure. The compounds all share a basic carbon skeleton consisting of a furanone moiety with a butyl side chain at the 3-position and other substitutions at other points on the basic structure. The antifouling compositions are intended to be used to combat the settlement and subsequent growth of marine organisms on submerged surfaces such as boat hulls or oil and gas platforms. These furanones are said to be extremely active against fouling organisms, for example, such as invertebrates and bacteria.
International Patent Publication No. WO 96/29392 is directed to methods and culture media including furanones for inhibiting homoserine lactone (HSL) and/or acylated homoserine lactone (AHL) regulated processes in microorganisms, including bacteria, fungi and algae. The disclosed compounds are structurally related furanones having a basic furanone moiety with an alkyl side chain at the 3-position of the basic structure. The basic structure is preferably halogenated and has other possible substitutions that are disclosed in the patent document.
International Patent Publication No. WO 99/53915 discloses a method of inhibiting the growth of Gram positive bacteria using one or more furanones having a specified formula.
International Patent Publication No. WO 99/54323 demonstrates diverse side-chain functionalizations of fimbrolides (halogenated 3-alkyl-5-methylene-2(5H)-furanones).
International Patent Publication No. WO 01/68091 discloses that certain selected furanone compounds are suitable as antifungal agents for a range of fungi.
International Patent Publication No. WO 01/43739 provides compositions and methods for inhibiting two-component signal transduction systems with halogenated furanones and related 3-haloalkenones.
Furanone-like 5-membered ring compounds recently have been identified in varied microorganisms (i.e., not only marine microorganisms), as being universal signal compounds that, like acetylated homoserine lactones, are involved in quorum sensing, namely the process that allows microorganisms to assess their environment, such as the density of organisms that surround them. Unlike acetylated homoserine lactones, however, these furanone-like 5-membered ring compounds appear not to be species-specific, and they appear to be active in very diverse types of microorganisms. (See S. Schauder, et al., xe2x80x9cThe LuxS-Family of Bacterial Autoinducers: Biosynthesis of a Novel Quorum Sensing Signal Moleculexe2x80x9d, Poster Abstract presented at xe2x80x9cCell-Cell Communication in Bacteriaxe2x80x9d Meeting in Snowbird, Utah, Jul. 6-9, 2001.)
Consequently, halogenated furanone compounds, in particular, and possibly other structurally similar compounds, may act by competitively inhibiting these furanone-like 5-membered ring signal compounds. As the furanone-like signals are recognized by different types of organisms, the inhibitory activity of, for example, the halogenated furanone compounds (and other compounds like them), interfere with growth and biofilm formation of various Gram positive and Gram negative bacteria, as well as of yeasts and fungi. Therefore, hereinafter, when using the term xe2x80x9cfuranonexe2x80x9d in this application, we have in mind those furanones, such as halogenated furanones and furanones noted in the patent documents discussed earlier, which exhibit such inhibitory activity.
While furanones are more friendly to the environment since they are derived from a naturally-occurring group of compounds that can be isolated from red marine algae, such as Delisea fimbriata, Delisea elegans and Delisea pulchra, they can be expensive to use in the amounts necessary to be effective in antimicrobial cleaning compositions.
Accordingly, there is a need for antimicrobial compositions that are friendly to the environment, effective and relatively economical to manufacture on a commercial scale for both domestic and industrial cleaning applications.
Surprisingly, we have found that an unexpectedly high level of synergy occurs in antimicrobial compositions that contain at least one furanone in combination with other disinfectants, such as, for example, at least one quaternary ammonium compound and at least one quaternized organosilane. The synergy is evidenced by the small quantities of each of these compounds that need to be used to produce an effective antimicrobial composition. The necessary overall amount of the compounds is less than that which would be required if any of the compounds were to be used on their own. In particular, it is possible to use small amounts of furanones, which can be expensive but are environmentally friendly, with small amounts of quaternized organosilanes which are also expensive, and quaternary ammonium compounds which are not particularly environmentally friendly but are quite effective antimicrobials. We believe that a similar type of synergy would be apparent in antimicrobial compositions that contain at least one furanone in combination with at least one quaternary ammonium compound or at least one quaternized organosilane. Similarly, we believe that biguanides and disinfectant amines also may be advantageously combined with furanones in an antimicrobial composition.
Accordingly, one aspect of the invention provides a composition comprising: (a) a sparing amount of at least one furanone; and (b) a sparing amount of at least one stable quaternized organosilane, wherein the amount of each of components (a) and (b) is sufficient to form, in combination, a synergistic, antimicrobial composition. Alternatively, another aspect of the invention provides a composition comprising: (a) a sparing amount of at least one furanone; (b) a sparing amount of at least one quaternized organosilane; and (c) a sparing amount of at least one quaternary ammonium compound, wherein the amount of each of components (a), (b) and (c) is sufficient to form, in combination, a synergistic antimicrobial composition. In yet another alternative embodiment, a composition of the invention comprises: (a) a sparing amount of at least one furanone; and (b) a sparing amount of at least one quaternary ammonium compound, wherein the amount of each of components (a) and (b) is sufficient to form, in combination, a synergistic antimicrobial composition.
In still another alternative embodiment, a composition of the invention comprises: (a) a sparing amount of at least one furanone; and (b) a sparing amount of at least one disinfectant selected from the group consisting of a quaternized organosilane, a quaternary ammonium compound, a disinfectant amine, and a biguanide, wherein, the amount of each of components (a) and (b) is sufficient to form, in combination, a synergistic antimicrobial composition.
Our invention also provides a method of cleaning a surface, or a reservoir or conduit that is fluid-filled using a synergistic antimicrobial composition comprising any of the combinations of components described above.